Hierarchy of credibility:
- Academic books
- Manufacturer’s white papers & internally published papers
- Web blogs
Manufacturer’s white papers may not be considered as credible as journals or conference papers as there will be a degree of bias toward their own service or product. The white paper will also likely not have gone through the same level of review, probably not by a panel of experts.
Wikipedia is not considered an academically credible source as it is updateable for any member of the public and although it can be peer reviewed it is not subject to rigorous review like conference papers or journal submissions.